Mammograms don't reduce risk of death: study

Death rates from breast cancer are the same for women who have mammograms as for those who don't, according to a large study.

Researchers from the University of Toronto studied 90,000 women over 25 years and found women who had mammograms had the same chance of death as women who had breast checks from trained nurses.

They also found that one in five of the breast cancers picked up by mammograms were "over-diagnosed", which means they were not a threat to the woman's life and did not need to be treated with chemotherapy, radiation or surgery.

One in 242 women who had mammograms were found to have had unnecessary cancer treatment when the tumour would not have affected their health.

Ductal carcinoma in situ (DCIS) is a cancer of the milk duct. So far doctors have struggled to accurately predict whether cases are likely to spread into the breast or not. As a result, it is often treated with surgery, such as mastectomy.

The study, led by Dr Anthony Miller from the University of Toronto, randomly assigned women aged 40 to 59 to either have regular mammograms, breast exams from trained nurses, or breast exams alone.

They found the women who had mammograms experienced no benefits.

Dr Alison Butt, director of research investment at the National Breast Cancer Foundation, told ninemsn this study highlighted the need for continued analysis and evaluation.

"This is one study. It has shown no benefit of breast screening, but many other studies have shown a significant benefit," she said.

"This study adds to the debate and continual analysis, but I don't think we should be thinking about changing guidelines or changing behaviours based on this study."

Dr Butt said there was no doubt that early detection gave women a better chance of survival.

"Continue to be breast aware and know what is normal for you," she said.

"If you are over the age of 50 to engage in regular breast screening."

Dr Butt said researchers were trying to find a way to determine which types of DCIS breast cancer needed to be treated and which ones could be left alone.

"If you start treating DCIS that doesn't need to be treated, women have to go through difficult treatment, which comes with psychological harm," she said.

"We're trying to tailor breast screening to be a lot more effective."

Professor Ian Olver, CEO of the Cancer Council, told ninemsn that it was important to remember that this was just one study out of nine into the same thing.

"All the Australian mammographic studies showed a benefit in terms of survival in the order of 21 and 28 percent advantage in terms of saving people from dying from breast cancer," he said.

"On balance, if you look at the whole fleet of studies we would still advise women between the ages of 50 and 74 have mammograms every two years."